153 
TAB. CCLXXYV. 
CALX_ carbonata. 
Carbonate of Lime. 
Div. 1. Crystallized. 
Tue perhaps numberless variations in the forms of the 
crystals of Carbonate of Lime, however difficult they may at 
first be considered by many, are one of the surest proofs of 
the necessity of attending particularly to their formation ; for 
when we are a little conversant with them, they seldom fail to 
indicate the place to which a specimen should be referred. 
The present variety is formed of two regular hexaédral 
pyramids applied base to base, each terminated by the faces 
of the equiaxe rhomb—see tal. 34—the alternate solid 
angles near the summit, being bevelled, form the little that 
remains of the metastatic variety—see ¢al. 33. The inci- 
dence of the three edges of the termination on the cor- 
responding edges of the pyramid is about 122°, that of the 
face of termination on the other three is nearly 133°, and 
the two pyramids on each other about 145°. The crystals 
are apt to vary a little, especially those in the next plate, 
for which these measures will serve. 
The right hand geometrical figure in this plate shows the 
position of the primitive rhomb in the centre, and the left 
hand one shows the oblique base of the curious mackle that 
belongs to this modification, to assist in the explanation of 
the next plate. 
The crystals are extremely neat on this specimen, which 
is in the possession of Mr. Lowry, whose remarkable abi- 
lities are so well known. It came from Ecton-mine, in 
Staffordshire. The same gentleman has a group of crystals 
of the same form from nearly the same spot; one crystal 
about ten inches in circumference, and nearly as long. 
